It used to be the case that you can send a maximum of 50 messages per second via the API. So you would need to include some waiting time if you need to send more messages. However, latest versions of the API have a pacing function built-in. So it would not help if you include any waiting time when you send your messages. In my case: even though the pacing function is there, I still include some waiting time in case I send a batch of messages that is longer than 50 messages.
